BEST PRACTICES

DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention National Institute for Occupational Safety and Health This document is in the public domain and may be freely copied or reprinted.

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Workers who handle diacetyl or work in areas where diacetyl exposure occurs are at risk of developing severe lung disease if their exposures are not properly controlled. The National Institute for Occupational Safety and Health (NIOSH) has developed guidance in a variety of areas to reduce workers’ exposures to diacetyl through engineering controls, best work practices, and techniques for monitoring airborne diacetyl exposures. Although these guidelines emphasize diacetyl, they can be applied to reduce exposures to diacetyl substitutes such as 2,3-pentanedione and other alpha-diketones.

DESCRIPTION OF EXPOSURE AND HEALTH EFFECTS

Flavorings are substances that alter or enhance the taste of food. They are composed of various natural and manmade chemicals and may consist of a single chemical, but more often they are complex mixtures. Workers in the flavorings production industry may be exposed to these substances in the form of solids, liquids, or vapors. Although thousands of flavoring ingredients are in use, little is known about most of these in terms of worker health effects, and few have occupational exposure guidelines such as recommended exposure limits (REL), permissible exposure limits (PEL), or threshold limit values (TLV)®.

NIOSH investigations have found that workplace exposure to diacetyl can result in reduced lung function and also cause a severe lung disease known as obliterative bronchiolitis. In obliterative bronchiolitis, inflammation and scarring occur in the smallest airways of the lung and can lead to severe and disabling shortness of breath. Symptoms include cough and shortness of breath on exertion. Obliterative bronchiolitis is an irreversible lung disease whose symptoms typically do not improve when the worker goes home at the end of the workday, on weekends, or on vacations. Obliterative bronchiolitis can reduce lung function enough to cause disability.

Occurrences of obliterative bronchiolitis were observed in the microwave popcorn industry in 2000 when eight workers were diagnosed with the disease after exposure to vapors from artificial butter flavoring ingredients including diacetyl [Akpinar-Elci et al. 2004a; Kreiss et al.

2002]. Several workers in flavoring manufacturing facilities were also diagnosed with obliterative bronchiolitis or severe fixed obstructive lung disease [CDC 2007]. Studies in four microwave popcorn plants found that a history of working as a mixer and higher cumulative exposure to diacetyl were associated with decreased lung function [Lockey et al. 2009]. In one Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione flavoring manufacturing plant, nearly one third of workers had restrictive breathing abnormalities [NIOSH 2011a]. This suggests that workers exposed to diacetyl and other flavoring ingredients could potentially develop a range of occupational lung diseases.

More recently, facilities have begun producing or working with substitutes for diacetyl, such as 2,3-pentanedione [Day et al. 2011; Boylstein 2012]. 2,3-Pentanedione, a 5-carbon alphadiketone, is chemically very similar to diacetyl, a 4-carbon alpha-diketone. Reports on the toxicity of 2,3-pentanedione were first published in

Abstract

form in 2010 [Hubbs et al. 2010;

Morgan et al. 2010]. Acute inhalation exposures to 2,3-pentanedione cause airway epithelial damage that is similar to diacetyl in laboratory studies [Hubbs et al. 2012]. In 2-week inhalation studies in rats, 2,3-pentanedione caused proliferation of fibrous connective tissue in the walls of airways, and projections of fibrous connective tissue sometimes extended into the air passageways [Morgan et al. 2012a,b]. Preliminary data suggest that repeated exposures to either 2,3-pentanedione or diacetyl can cause airway fibrosis in rats [Morgan et al. 2012a]. In the acute inhalation study of 2,3-pentanedione, changes in gene expression were noted in the brain [Hubbs et al. 2012]. As a group, these results raise concerns that the toxicologic effects of diacetyl may be shared with other alpha-diketones, which are close structural analogs. Additional alpha-diketones of interest include but are not limited to those used in food manufacturing such as 2,3-hexanedione and 2,3-heptanedione. Diacetyl substitutes should not be assumed to be safe until toxicology studies are performed.

It is difficult to quantify the number of employees involved with flavor manufacturing and, more specifically, those who have diacetyl or diacetyl substitute exposure in the United States.

According to the Environmental Protection Agency Non-Confidential Inventory Updating Report, diacetyl had an aggregate production volume between 10,000 and 500,000 pounds in 2002 [EPA 2002]. The North American Industry Classification System (NAICS) category 311, the most relevant category, includes subcategories Flavoring Syrup and Concentrate Manufacturing (NAICS Code 311930), Spice and Extract Manufacturing (NAICS Code 311942) and All Other Miscellaneous Food Manufacturing (NAICS Code 311999). In 2002, 21,000 workers were employed in facilities classified under 311930 and 311942 [Department of Commerce 2004]. According to the Flavor Extract Manufacturers Association, whose members account for approximately 95% of all flavors produced in the United States, a total of 6,520 employees work directly in the flavor manufacturing or laboratory activities in membership companies [Hallagan 2010].

In addition to workers who were exposed to diacetyl during its production or addition to flavored substances, health effects have also been observed in workers with downstream exposure to diacetyl from those flavored substances, including workers in areas such as quality control and packaging products within microwave popcorn facilities [Kanwal et al. 2006].

In 2010, California promulgated a regulation for occupational exposure to food flavorings containing diacetyl that requires installation of exposure controls to reduce exposures to the lowest feasible levels. In 2012, the American Conference for Governmental Industrial Hygienists published a threshold limit value® of 0.010 parts per million (ppm) 8hr-time weighted average (TWA) with a short-term exposure limit (STEL) of 0.020 ppm for diacetyl [ACGIH 2012].

Diacetyl and 2,3-pentanedione are monitored using personal and area air samples because the predominant route of exposure is inhalation. Studies conducted by NIOSH researchers [NIOSH 2008a,b,c] and Martyny et al. [Martyny et al. 2008] describe common tasks performed by workers in the production of flavorings. Results of these surveys illustrate how sampling can identify emission sources and guide corrective actions.

Personal breathing zone sampling is the preferred method for estimating the exposure of a worker. To collect a breathing zone sample, the Occupational Safety and Health Administration (OSHA) states that the air sampling collection media be attached “to the shirt collar or as close as practical to the nose and mouth of the employee’s breathing zone” [OSHA 2008a]. For personal sampling, a worker is outfitted with the air sampling equipment, and the inlet to the collection media is positioned within the worker’s breathing zone. Area sampling can be performed for several purposes such as to evaluate exposure characteristics associated with a work area or process or to determine the efficacy of control systems. While the same sampling equipment and analytical procedures may be used in some cases for personal and area sampling, area sample results represent air concentrations at a fixed location. In contrast, personal sample results represent worker exposure averaged over the selected sampling period. The development of a comprehensive sampling strategy to assure selection of representative employees, appropriate work areas and proper sampling periods (time-weighted average vs short-term exposure limit sampling, etc.) should be done in consultation with a qualified professional. Sampling for diacetyl and 2,3-pentanedione as a vapor and a particulate (when present) should be considered because these compounds may be found in both phases.

SAMPLING AND ANALYSIS FOR DIACETYL VAPOR

Chemists at NIOSH and OSHA have developed a variety of sampling and analytical methods for determining concentrations of airborne diacetyl vapor. Selection of a method to use in any given situation should be made after consultation with an analytical laboratory accredited by the American Industrial Hygiene Association for analyses. Only qualified professionals should collect samples.

OSHA Method 1013 can be used simultaneously for diacetyl and acetoin [OSHA 2008b].

Samples are collected through two 600 mg tubes that contain specially cleaned and dried silica gel in series at 0.05 L/min for 180 minutes for a time-weighted average (TWA) concentration or

0.2 L/min for 15 minutes for short-term concentration. Samples are extracted with an ethanol solution and analyzed by GC-FID.

OSHA Method 1012 is more sensitive and can also be used to analyze for diacetyl and acetoin for either a 180-minute or 15-minute sample [OSHA 2008c]. OSHA Method 1012 utilizes the same sample collection media and conditions as OSHA Method 1013. Prior to analysis, the extract is derivatized and analyzed by gas chromatography with electron capture detection to produce a tenfold increase in sensitivity.

Best Practices: Engineering Controls, Work Practices, and Exposure Monitoring for Occupational Exposures to Diacetyl and 2,3-Pentanedione

SAMPLING AND ANALYSIS FOR 2,3-PENTANEDIONE VAPOR

OSHA Method 1016 can be used to measure 2,3-pentanedione concentrations [OSHA 2010]. Samples are collected through two 600 mg tubes containing specially cleaned and dried silica gel in series at 0.05 L/min for 200 minutes for a TWA concentration or 0.2 L/min for 15 minutes for short-term concentration. Samples are extracted with ethyl alcohol:water solution and analyzed by GC-FID.

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